1. Field of the Invention
The present invention relates to a method of producing an aqueous solution of the active inorganic materials extracted from rocks, particularly, granite.
Although commercially available inorganic materials usually called xe2x80x9cmineralsxe2x80x9d have hitherto been produced individually or in the form of a mixture, a technique by which active inorganic materials can be extracted directly from rocks in aqueous solution has not yet been known in the art.
2. Disclosure of the Prior Art
Nowadays, according to the development of industries, natural resources become gradually consumed and drained, resulting in the extreme desolation of the natural environment. Thus, human beings are suffering from and faced with severe natural difficulties and disasters such as a sharp decrease of agricultural harvests, a shortage of drinking water, and so forth. Several studies and efforts have been somewhat helpful to diminish or surmount such difficulties and disasters. However, there still remain many resources to be exploited for improving the life of human beings. For example, many rocks such as granite are being used as aggregate or raw materials for public works and construction. These rocks have been disregarded with respect to their significance. Certain secondary resources useful for the life of human beings can be obtained from them. As is well known, many kinds of inorganic metal components are abundantly contained in the rocks.
The object of the invention is to provide a method of treating stone or rocks, particularly, granite, which are scattered throughout the country, to extract inorganic metal components from the rocks.
Another object of the invention is to obtain inorganic metal components useful as mineral sources to be supplied to soils, animals, plants or the human body and useful in industrial facilities such as water or wastewater-purifying or treating facilities.
The above objects can be achieved by the method according to the present invention, which comprises charging an extracting vessel with finely divided granite at ambient temperature and pressure; introducing an aqueous ammonia solution with agitating and then diluted sulfuric acid into the vessel; introducing 98% ethyl alcohol (C2H5OH) into the vessel at below 80xc2x0 C. so as to elevate the internal pressure of the vessel to 2 to 3 kg/cm2 for facilitating the formation of complexes; and then agitating the resultant reaction mixture for 20-160 minutes at 80xc2x0 to 85xc2x0 C. while maintaining the inner pressure of the vessel.
A chemical analysis of a raw rock, granite, which is widely available in Korea, is shown in Table 1 below.
For the sake of convenience in handling, the finely divided granite preferably has an average particle size of about 80 to 100 mesh. As generally well known, the solubility of ammonia gas (NH57) in water is about 33.1% (by weight) at ambient temperature (20xc2x0 C.). Generally, about 30% aqueous ammonia solution is commercially available. Therefore, this solution may be used in performing the present invention as it is. However, the ammonia solution, the solubility of which is diluted to 15 to 20%, may also be used in consideration of its cost or reactivity. Sulfuric acid is available in various concentrations ranging from 78% to 100%, but about 23% to 30% sulfuric acid giving a higher activity is preferably used in the present invention in view of its costs.
Generally, ammonia has an ability to form a coordinate covalent bond or an ion-dipole bond with the molecules or ions capable of accepting electron pairs; thus it can create numerous complexes by so-called xe2x80x9cammonization.xe2x80x9d The aqueous ammonia solution (ammonia water or aqua ammonia) contains the molecular species, NH3 and NH4OH (ammonium hydroxide), NH4+, OHxe2x88x92, etc. In the present invention, the ammonia water is employed to pre-treat the raw material so that inorganic metal ions can form complex ions with NH3, H2O, OHxe2x88x92 or the like, which are the ligands of the complex salts isolated from the granite. On contacting the inorganic metal ions, the ammonia water dissociates and reacts with the metal ions as shown in Equations 1 and 2 below.
Equation 1:      2    ⁢          NH      4        ⁢    OH    →            NH      4      +        +                  H        2            ⁢      O        +          2      ⁢              OH        -              +          H      +      
Equation 2:                    4        ⁢        MO            +              4        ⁢                  NH          4                ⁢        OH              →                  2        ⁢                              M            ⁡                          (              OH              )                                2                    +                                                  M              2                        ⁡                          (                              NH                4                            )                                4                ⁢                              (            OH            )                    4                      ,
wherein M is a bivalent metal ion. For example, a reaction of the ammonia water with aluminum oxide can be shown as follows:
Al2O3+NH4OHxe2x86x92Al(OH)3+Al(OH)x(NH3)y+H3O++OHxe2x88x92, 
wherein x+y=4, 6 or 8.
Treatment of the rock with ammonia water is desired for preventing the inorganic metal ions from being linked with strong field ligands such as Co (II or III), CNxe2x88x92, NO2xe2x88x92 and the like, which may be present in the raw rock. Since the inorganic metal complexes formed by the reaction with such strong field ligands are very stable and have low reactivity, they are undesirable for the purpose of the present invention. Therefore, according to the invention, the raw material is treated so that the inorganic metal ions can be captured in the form of complexes with the low field ligands such as H2O, NH3, SO4xe2x95x90 and so forth, as described hereinbelow. It is believed that the addition of sulfuric acid permits the inorganic metal ions to produce various types of complexes other than the usual sulfates in the form of normal, acidic and basic salts. In view of the coordinate covalent bond theory, such complexes may be shown as follows; however, the types of complexes are not critical in the present invention:
Mam[Mbn(SO3)x(SO4)y]z
Mam[(SO3)x(SO4)y]z
[Mam(SO3)x](SO4)yMbn(SO4)y
Mam[Mbn(NH3)x(SO4)]z
Mam[(NH3)x(SO4)]z
Mam[Mbn(H2O)x(SO4)y]z
Mam[(SO3)x(NH3)y]SO4
Wherein:
Ma is an inorganic metal (complex) ion;
m is the number of the inorganic metal ions;
Mb is another inorganic metal ion;
n is the number of inorganic metal ions;
x, y are each the number of ligands or complex ions; and
z is the number of free ions
Important complexes are exemplified as follows:
Al2[Fe(SO3)4(SO4)2]2
Fe2[(SO3)4(SO4)2]2
Al2[(SO3)4(SO4)]3
Al2(SO4)3
Al2[Fe(NH3)4(SO4)2]2
Fe2[(NH3)4(SO4)2]2
Mg[Fe(H2O)4(SO4)2]2
Fe[(SO4)2(NH3)4]SO4
The way of reading a complex is schematically illustrated below: 
Quantitative and qualitative analyses for respective inorganic metal cations, free radical anions, and ligands may be performed according to a general chemical quantitative and qualitative analytical method. Particularly, in the case of a metal cation, it can easily be detected by an atomic absorption spectrometry, inductively coupled plasma spectrophotometry (ICP) and so forth. Anions such a sulfate ion can also be easily detected by an ion chromatography.
When the reaction is completed, ethyl alcohol is recovered through a condenser for recycle. When the internal pressure in the extraction vessel drops to ambient pressure, the resulting crude liquid product is transferred into an acid-resistant tank through a discharging port with continuously operating an agitator. This crude product is then passed through a filter press to perform a solid-liquid separation, resulting in the formation of the desired clean mineral liquid in which inorganic metal ions are present in solution. The concentration of the total salts present in the mineral solution so obtained may simply be determined by comparing it with the concentration of a reference solution according to a conventional method using a refractometer. Upon being determined by this method, the concentration of the total salts in the mineral solution of the present invention has been found to be about 30 to 40% by weight on average.
The sludge which is formed as a by-product from the solid-liquid separation can also advantageously be utilized without disposal. The sludge contains plenty of mica, silicates, silica, and so forth which can also be easily recovered. The recovered mica is baked so that it can be used as a heat-insulating material, radioactivity absorbent, feed stuff additive, soil modifier, and so forth. The silicates so recovered, after being purified, are useful as additives for paints, or materials for silicone rubbers, silicon oils, and the like. The silica is useful as a building material or interior finishing material. Further, the residues themselves from the solid-liquid separation can be used as a mineral fertilizer, soil modifier, and the like. Therefore, the method according to the present invention may be called a clean technique which is free from environment contamination.